Razorback sucker rescue may be working
Leaving more water in overtapped Western rivers looms as a key for saving imperiled fish species, a strategy that’s showing success with the razorback sucker — a fish with a bony cranial bump. It can grow 3 feet long and swim 450 miles if flows are sufficient.
U.S. Fish and Wildlife Service biologists counted 50 yearling razorbacks during a recent survey in the upper Colorado River Basin — the result of water releases in 2016 and 2017 from the Navajo Reservoir aimed at helping the fish, agency officials said this week.
Federal operators of the reservoir let out 5,000 cubic feet of water per second for 50 days, more than doubling regular flows in the San Juan River. This increased flow created nursery pools, the habitat razorbacks and three other endangered native fish need to spawn and survive.
But controversy still surrounds the federal government’s plan to upgrade the razorbacks’ status from endangered to threatened — meaning extinction is slightly less imminent — based on evidence
they’re reproducing in the wild. The feds also plan to reclassify the humpback chub, another imperiled Colorado River species.
Hundreds of thousands of razorbacks once flourished across the Colorado River Basin, migrating through a seven-state area before dams disrupted their world.
Agriculture, expanding cities, power plants, snowmaking for skiing, fossil-fuel extraction and other industries harnessed the river and its tributaries. Some cities, including Denver, are preparing to divert more water out of the Colorado if necessary to enable population growth.
Saving razorbacks and other fish “is going to be totally dependent “on putting more water into rivers, said Tom Chart, director of the Upper Colorado River Endangered Fish Recovery Program, a 25-year, $360 million government-run rescue effort.
“We’re not going to be able to restore the natural hydrological conditions. We understand that,” Chart said. “But we can recreate conditions that help young fish much more regularly.”
Yet the intensifying climate shift toward heat and aridity in Southwestern states, combined with population growth, constrains biologists’ push to put more water into rivers for environmental purposes.
No water could be released this year from the Navajo Reservoir, which straddles Colorado and New Mexico and holds 1.7 million acre-feet, Bureau of Reclamation engineer Susan Behery said. Probably none will be spared next year, either, because water managers are prioritizing storage after a near-record low snow year left the reservoir half full.
Raising, stocking razorbacks
For more than 30 years, federal biologists responsible for emergency rescues of endangered species have relied on raising razorbacks in hatcheries and copiously stocking them into Colorado River tributaries. Razorbacks evolved in wild freeflowing rivers, enduring for millions of years, until widespread dams and diversions reduced and regularized nature’s fluctuating flows. The razorback had nearly blinked out by 1980, with only 100 survivors — weakened by the disruption of flows and attacked by non-native predators such as bass, walleye and pike that state wildlife agencies have introduced for recreational sport fishing.
Federal agencies over the last 18 years have raised and stocked Colorado River Basin waterways with 587,000 razorbacks, said Julie Stahli, U.S. Fish and Wildlife biologist and database manager.
The human demands for more water are such that wildlife managers have had to focus on threats they can try to control, such as the attacks on natives by nonnative predators. Eradication patrols have proved successful, though sport fishermen sometimes object.
Under the Endangered Species Act, the government is required to ensure a self-sustaining population of razorbacks. Reclassification of endangered fish as merely “threatened” would increase the ability to tap Colorado River Basin waterways for human purposes.
Federal survey crews counted the 50 yearling razorbacks along the San Juan River downriver from the Navajo Reservoir. That’s the most fish counted since the surveys began two decades ago. Fish and Wildlife Service biologists calculated that this many yearlings could mean there are thousands of razorbacks along a 180-mile stretch of the river before it reaches Lake Powell.
Navajo tribal biologists have embraced the effort to save razorbacks and other imperiled native fish. A Navajo team this year helped move 300 razorbacks over a barrier for spawning while weeding out non-native predators.
“We are trying to preserve the razorback for our future generations,” said Navajo fish biologist Jerrod Bowman. “So that our kids can see razorbacks . ... Our numbers are really looking great.”
“Far from the self-sustaining populations”
The problem with officially upgrading the status of fish, Bowman said, is that just the presence of yearlings may not establish that a species has become selfsustaining as required. Razorbacks usually don’t reproduce until they’re at least 2 years old. Adults can live up to 40 years.
Under President Donald Trump, federal wildlife officials have faced pressure to upgrade and de-list endangered species when scientists still aren’t certain about survival, said ecologist Taylor McKinnon, a public lands campaigner for the Center for Biological Diversity.
“The news of razorback yearlings in the San Juan River is certainly welcome. But we’re still far from the self-sustaining populations that the recovery plan envisions,” McKinnon said, warning of still-marginal habitat conditions that don’t favor wild-born fish.
“Drying rivers, given climate change, and climateworsening federal fossilfuel policies, also cast a long shadow over future recovery efforts,” he said. “Recovery depends on providing adequate river flows — flooding flows in the spring, and minimum base flows during the rest of the year.”
Tapping the Colorado River has catalyzed development of the West for 150 years. The river now serves as a primary source of water for 40 million people from the mountain headwaters northwest of Denver to California’s deserts.
Demand for water is so great that restoring natural, fluctuating flows long has been regarded as a luxury. Federal biologists initially worked at simulating small floods and recreating sidechannel pools for razorbacks. Reservoir operators sometimes find the flexibility to release water to help fish. But opportunities to do so have been limited amid urban population and industry expansion.
At Fish and Wildlife Service regional headquarters west of Denver, Chart said he hopes to rely less on hatcheries and stocking of razorbacks so that tanks can be redeployed for recovery of the more-endangered bonytail chub and Colorado pikeminnow fish.
“This is a heavily regulated river system. And the climate change signals? It is going to be warmer, potentially drier. We’re trying to recover fish and also respect water development,” Chart said.
“We’re going to continue to try to control the non-native competitors . ... But river flow management is going to be critical. We will be working with water managers. We feel like we have turned a corner. We’ve built up the adult populations. They are spawning at many locations. And now we’re starting to get the young fish.” Bruce Finley: 303-954-1700, bfinley@denverpost.com or @finleybruce